Sand and us

December 18, 2013

I have been offline for a while, living the life of a hermit attached to a word-processor, surrounded by a veritable chaos of index cards, large sheets of paper covered in my version of ‘mind-maps’, magazine clippings and journal articles, all of which required consolidation into some kind of coherent story. More of this later, but I had not completely removed myself from the real world and last week, when I happened upon a BBC news story titled ‘Sumatra coastal cave records stunning tsunami history’, I thought that this was a sand story that had to be told, a perfect opportunity to return to posting.

I wrote a couple of pieces in the aftermath of the 2011 Tōhoku-oki earthquake and tsunami, discussing some of the fascinating research that was going on and wondering why the geological record of tsunami events along that part of the Japanese coast had been so flagrantly and catastrophically ignored. The testaments of past tsunamis around the world (together with earthquakes and, indeed, hurricanes and volcanic eruptions) demonstrate with irrefutable clarity the utter nonsense of talking about a ‘hundred year’ or a ‘five hundred year’ event and the tragic consequences of incorporating such assumptions into any kind of planning process.

Jessica Pilarczyk is a member of an international team that has investigated the sediment records of past tsunamis, including the Jōgan event of A.D. 869 that devastated the Sendai coastal plain to essentially the same extent as the tsunami of 2011, yet seems to gone missing from the minds of Japan’s nuclear facility planners. Now, at the recent meeting of the American Geophysical Union, Pilarczyk and her colleagues have described their findings from an extraordinary cave on the Sumatran coast. Situated above modern tide levels, the cave is nevertheless filled with layer after layer of sand, separated and sealed by layers of bat guano (the innocuous looking dark layers in the trench in the photo above). Storm deposits? Unlikely, because, as Pilarczyk’s meticulous analysis has shown, the sand contains the shells of microscopic marine creatures, foraminifera, that live only on the seafloor where the water depth is greater than 20 meters – well beyond the ability of waves to scour the sediment, even in the biggest storms. The sand can only have been excavated from the sea bed by a tsunami, carried inland and dumped in the cave. The oldest tsunami sand dates from around 7,500 years ago, but the most recent is 3,000 years old – the cave filled up, there was no longer room to dump more sand and so younger deposits, including the debris from 2004, were instantly eroded. The bat excrement preserved the older record, but of course today’s inhabitants of the cave make it a less than delightful place to work; I have spent time in bat-infested caves in the rain forests of Kalimantan and can vouch for the challenges of such an environment.

But the work and the results are extraordinary – more than 4,000 years of detailed tsunami records, dated and documented. It’s a story that should be required reading for anyone delusional enough to believe in the ‘five hundred year’ event, and certainly for everyone upon whose actions people’s lives depend. The Sumatran cave record reveals a period of 2,400 years during which there were no tsunamis, followed by a sequence of five in 400 years.

A cave on the northwestern coast of Sumatra holds a remarkable record of big tsunamis in the Indian Ocean.

The limestone opening, close to Banda Aceh, retains the sandy deposits washed ashore by huge, earthquake-induced waves over thousands of years.

Scientists are using the site to help determine the frequency of catastrophes like the event of 26 December 2004.

This is being done by dating the cave's tsunami-borne sediments, which are easy to see between layers of bat droppings.

"The tsunami sands just jump right out at you because they're separated by guano layers. There's no confusing the stratigraphy (layering)," explains Dr Jessica Pilarczyk.

"It makes for interesting field work; I'm not going to lie to you. The bats get very excited when people are disrupting their space. But from a geologist's point of view, this cave has the most amazing stratigraphy," she told BBC News.

She is part of a team of researchers - led by Prof Charles Rubin - from the Earth Observatory of Singapore, an institute of Nanyang Technological University that is investigating the coastal history of Indonesia's largest island.

Sumatra's proximity to the Indo-Australia and Sunda tectonic plate boundary, and the giant earthquakes that occur there, means its shores are at risk of major inundations.

Understanding how often these occur is important for policy and planning in the region.

The Acehnese cave lies about 100m back from the swash zone at current high-tide. Its entrance is also raised somewhat, and this prevents all waters from getting into the opening - apart from tsunamis and severe storm surges.

Dr Pilarczyk and colleagues have dug trenches through the alternating bands of bat guano and sand to piece together the cave's history.

The scientists know they are looking at tsunami deposits because they can find debris in the sediments of seafloor organisms such as microscopic foraminifera. Only the most energetic waves could have lifted and carried this material into the cave.

The investigations are ongoing but the team thinks it can see deposition from perhaps 7-10 tsunamis. The geometry of the cave means these events would likely have been generated by earthquakes of Magnitude 8, or more. By way of comparison, the devastation wrought by 26 December 2004 stemmed from a M9.2 tremor.

Dating the old deposits is obtained by radiocarbon analysis of organic debris caught up in the bands, such as molluscs and pieces of charcoal from old human-lit fires.

Work is under way to date even the insect remains eaten by the bats and now immersed in the guano layers.

Today, the cave is so full of sand and bat droppings that any new event will essentially overwash and erode the most recent deposits. "The 2004 tsunami completely inundated the cave," comments Prof Rubin.

Nonetheless, the stratigraphy from about 7,500 to 3,000 years ago is impeccable.

"What we think we have is actually a near-complete sequence of late-Holocene deposits. This is amazing because usually the records we have are fragmentary at best. This coastal cave is a unique 'depocentre', and it's giving us a remarkable snapshot of several thousands of years, allowing us to figure out every single tsunami that would have taken place during that time," said Dr Pilarczyk, who is affiliated also to Rutgers University, US.

The team's other investigations along the Acehnese coast are filling in the period from 3,000 years ago to the present.

And the take-home message from all this research is that the biggest tsunamis are not evenly spaced through time. Yes, there can be long periods of quiescence, but you can also get major events that are separated by just a few decades.

Co-investigator Prof Kerry Sieh says this is a cautionary story.

"2004 caught everybody by surprise. And why was that? Because nobody had been looking back to see how often they happen, if they'd ever happened," he told BBC News.

"In fact, because people thought they had no history of such things, they thought it was impossible. Nobody was prepared, nobody had even given it a second thought. So the reason we look back in time is so we can learn how the Earth works and how it might work during our watch."

The cave research also involves scientific input from Syiah Kuala University in Banda Aceh.

Going to the beach is awesome; getting sand in your house and car, not so much. It’s funny how a great afternoon playing in the sand and running in the waves can be dampened when you realize how much of a mess you’ve made tracking all that sand back inside with you. It almost looks like you tried to bring the beach home. Fortunately, there are a few ways to prevent your car and house from looking like a hurricane hit them by getting the sand off your feet after you leave the beach. Some are inventive, some are obvious classics, but they’re all worth incorporating into your next beach day.

Baby powder

Seriously. Toss a bottle of baby powder into your beach bag and get ready to have your life changed. When you leave the beach, apply a nice heap of powder to your feet and rub it in. This absorbs the moisture that’s causing the sand to stick to your feet, and you’ll be able to brush off the excess and walk away. Plus, now your feet smell nice and clean.

Portable water supply

One of the best ways to wash sand off your feet is to use, well, water. A lot of beaches have shower-type stalls where the sand meets the parking lot and you can spray down your legs and feet and knock off the worst of the dirt. Sometimes, though, that’s not enough. (And sometimes you’ll still have to cross some sand to get to your car, in which case, you’re back to square one.) The solution? Pack a small plastic tub and a big bottle of water before you go, then use them when you’re standing next to your car. It doesn’t take much; just enough for you to submerge your feet and rinse them down. Then you can towel off, dump the water and be on your way.

Welcome mats

This one’s so obvious that most people overlook it. Take a welcome mat with you — or buy one for the occasion that you can leave in the car — and set it down next to your vehicle before you get in. Use a towel to knock off the bigger chunks, then wipe your feet on the welcome mat to clear out the rest of the sand.

Dry sand

Dry sand can actually adhere to the wetter sand on your feet and help to remove it. It’s a little like how lint sticks to itself, so a ball of lint can help you clean the lint trap in your dryer. When you’re ready to leave, scoop up some dry sand and rub it along your feet and legs, making sure to rub it into the wet sand that’s stuck to you. The dry sand can help slough off the wet stuff, making it easier to just dust off your feet with a towel before you go.

Specialty products

Staying sand-free is such a problem that there are a growing number of specialty products available to help you clean up after a day at the beach. For example, Sand-Off uses a special mitt that comes with a powder built right in, so all you have to do is apply the mitt to the sandy part of your body, let the powder squeeze out and wipe away the sticky sand. It’s good for multiple uses, and it’s a small enough product that you can toss it in your beach bag and forget about it until you need it.

Keeping excess sand out of your car and house can feel like an endless battle during beach season, and there’s always the chance that you or your kids will track some home no matter what you do. However, with the right preparation, you can go home clean and happy and leave the beach behind.

July 24, 2013

As the residents of Breezy
Point continue on their path back to normality after the ravages of
superstorm Sandy, part of that normality is that Larry
Deemer has been out and about on the beach again, superbly documenting the
shape-shifting art of the sands. Here, many thanks to Larry, is a selection of his latest photographs –
enjoy!

July 10, 2013

A few years ago I
reported on my visit to San Francisco's Exploratorium, a place of wonder for,
as they say, “children of all ages.” It has now moved to a brand-new facility on
the city’s piers, and I have to admit that I am excited at the idea – as yet
that’s all it is – of seeing it. A number of the exhibits which, unsurprisingly,
I found particularly fascinating, were the works of Ned Kahn. On his website he has this statement:

The confluence of science and art has fascinated me throughout my career. For
the last twenty years, I have developed a body of work inspired by atmospheric
physics, geology, astronomy and fluid motion. I strive to create artworks that
enable viewers to observe and interact with natural processes. I am less
interested in creating an alternative reality than I am in capturing, through my
art, the mysteriousness of the world around us.

My artworks frequently incorporate flowing water, fog, sand and light to
create complex and continually changing systems. Many of these works can be seen
as “observatories” in that they frame and enhance our perception of natural
phenomena. I am intrigued with the way patterns can emerge when things flow.
These patterns are not static objects, they are patterns of behavior – recurring
themes in nature.

In my humble view, Kahn succeeds brilliantly and compellingly in capturing
“the mysteriousness of the world around us.” Go to his website and enjoy – and,
if you can, go to the Exploratorium.

June 11, 2013

Everyone I have talked to who saw even part of the
documentary recently shown in Europe expressed a common reaction: surprise.
Which was exactly the intention of Denis Delestrac and all of us who were
involved: sand as a non-sustainable resource?

Illegal mining of sand from rivers and beaches is rampant – and big
business – around the world, and nowhere more so than India. The courses of
rivers are changed, people’s livelihoods ruined, ecological havoc induced,
and there have been deaths. It is a major and complex issue for the country –
there is money to be made by local people and governments as well as by the
mafia. Attempts to shut down operations are often opposed, sometimes violently,
by villagers for whom the extraction of sand is an important source of income.

As a matter of curiosity, I browsed the internet news sources and, as a sign
of the scale and complexity of the problem, the following is but a sampling of
stories extracted from only the last month.

Sand policy a formality in
Hassan; mafia continues its rule

A sand policy is in place in the district to check illegal sand extraction
and to protect the interest of both the people and natural resources. However,
the district is in the grip of ‘sand mafia’ and the officials have turned a
blind-eye towards it.

Three rivers — Yagachi, Hemavathy and Cauvery — flowing in the district are a
boon not only for farmers but also for the sand mafia. The river beds are being
dug up day and night for the past few years to satiate the greed of the mafia.
At least a hundred sand-laden lorries leave for Bangalore every night. Political
leaders of all parties are behind the mafia, so, officials think twice before
taking any action. And, when they take action, the violators are alerted well in
advance, through their sources.

Hurt real estate sector reeling
under sand bans

MARGAO: The construction industry in Goa is reeling under a double whammy -
an economic slowdown-infused buyer's market and a debilitating shortage of
construction material, especially sand. While the state government has banned
the extraction of sand in Goa, the Karnataka
government has banned its transportation to Goa. These developments have led
to a severe scarcity of this fundamental construction material and an over 100%
escalation in its price. There's also a paucity of other construction materials
such as stone aggregate, rubble and laterite stones.

Authority pulls down sand mafia
bridge in Greater Noida

GREATER NOIDA: Toughening its stand against the sand mafia, the Gautam Budh
Nagar district administration on Friday demolished an illegal bridge put up by
miscreants near Gulavali village in Greater Noida.

On receiving a tip-off about the unauthorized bridge constructed to transport
illegally-mined sand, police and mining department personnel reached the spot
and took around five hours to pull down the bridge.Police said the men involved
in the illegal dredging of the river bed fled as soon as cops and department
officials reached the spot. Officials are trying to find out if similar bridges
have been made elsewhere.

Illegal sand mining: 32
tractors seized

Officials seized 32 tractors in Khammam district for illegal sand quarrying
in Sarapaka village in Burgampadu and Chintakani mandals on Saturday night and
Sunday.

The officials received information that some persons were illegally
transporting sand in 20 tractors in Sarapaka village.

Squads to check illegal sand
mining in district

PUNE: The district administration has appointed 13 squads, one for each
taluka, to keep a check on illegal
extraction of sand from rivers and its transportation following a rise in
the number of cases of illegal transportation of sand. Besides, staff has been
deployed at almost all check posts along the district border to identify sand
trucks entering or leaving without proper permits.

Illegal extraction of sand
is on the rise as most river beds in the district have gone dry due to water
scarcity. The administration has identified 340 extraction spots in the
district. However, sand extraction during the ongoing season is not permitted at
any of the spots, as all sites are awaiting environmental clearance.

"If any
such activity is under way in the river beds, it
is illegal," said an official of the district mining department. Officials said
that the administration has undertaken repeated drives to restrict illegal sand
mining. However, they said, staff on duty often faced stiff opposition from
people involved in illegal activities. Officials have also faced physical
assaults during raids and searches. Many a times extraction work is carried out
during the night and in remote spots, which makes it difficult for the poorly
equipped staff to initiate action, they said.

Tough cop shunted out at behest
of sand mafia

NANDIGAMA: The sand mafia seems to have flexed its muscles again and
succeeded in shunting out a sub-inspector who took them on in Nandigama, an area
that has emerged as a goldmine for sand smugglers.

SI S Ramakrishna had acted swiftly against sand contractors carrying out sand
poaching on the banks of river Krishna at Nandigama. But the officer's posting
in the town lasted only 40 days, thanks to the government allegedly buckling
under the pressure of the local sand mafia, which is said to be controlled by
politicians cutting across party lines.

Ghariyal population rising in
Chambal

LUCKNOW: The new ghariyal hatchlings at the national
chambal sanctuary give a boost to ghariyal conservation. After more than 100
ghariyals died in
Chambal between December 2007 and March 2008, their number has
increased to 785, at present, from 300-odd ghariyals three years back. One of
the major reasons why ghariyal population is going down is the destruction of
the habitat. Illegal sand mining and illegal fishing along the banks of Chambal
river destroy the habitat of ghariyals.

"These are the two direct threats to ghariyals," said DFO, Chambal national
sanctuary, Sujoy Banerjee. The illegal sand mining on the banks of the river
destroys the habitat of ghariyals and disturbs their basking area. More than
that, since ghariyals lay their eggs under sand beds, illegal sand mining
destroys their nests.

Activists seek substitutes for
sand

MUMBAI: Artificial
sand that is sand obtained by crushing stones and boulders is being
considered as an alternative to natural sand, said Swadhin Kshatriya, additional
chief secretary, revenue.

The objective in looking for an alternative, said
Kshatriya, was to reduce the dependence on natural sand and thus reduce
environmental degradation. Asked if artificial sand would not result in cutting
of hills, Kshatriya said at present it was the only technology
available.

"Sites will be chosen such that it causes minimum environmental
damage," he said.Sources said barren land will be considered for extraction
of stones and boulders. "Artificial sand is being used though at limited
construction sites. Its only drawback is that it does not give a good finish,"
said sources.

Activist
Sumaira Abdulali who has been fighting against illegal sand mining and has
been advocating an alternative to natural sand said the solution was even
worse.

"It would mean breaking down not just hills but mountains, denuding
trees and creating flat lands. This would result in huge climatic changes. When
we talk alternatives it must be recycling and not wreaking havoc," she
said.

Abdulali said in some Scandinavian countries no fresh building
materials are allowed in a redevelopment project until the existing debris is
entirely recycled. In England, slag (a by product of the metal industry) is used
to make precisely engineered aggregate suitable for construction.Natural
sand is mined from river bed and the sea-shore. To meet the demands of the
construction industry, river beds have been stripped of sand causing soil
erosion and flooding of fields close to river banks. The government recently
framed a new mining policy on the directions of the Supreme Court. No permission
for mining can be granted unless an environment clearance has been obtained.
While the state cabinet has approved the new policy it has been submitted to the
court for its nod, said revenue officials. Last year the government earned Rs
1,200 crore [~$200 million] as revenue from minor minerals. Another alternative
being considered is the silt from dams. "This will also increase the holding
capacity of dams. But this concept is still very preliminary," said sources. A
third alternative being considered is bricks from fly-ash which is a by-product
of thermal power plants. Kshatriya said the report was in its final stages and
will be submitted to the cabinet soon. Abdulali said the government must
consider recycling and invest in research. "It is for the government to ensure
that the alternatives become commercially viable," she said.

May 29, 2013

Sand: an investigation into a disappearance. Shown last night on ARTE, the
European culture channel, this superb documentary by Denis Delestrac has
already made waves. It has also provided me with a great deal of pleasure and
satisfaction – last year, Denis filmed a long piece of yours truly holding forth
on the topic and extracted a number of choice selections for inclusion in
the documentary. So, last night, for the first time, I sat and watched myself on
TV…..

The film also includes wise words from, amongst others, Orrin Pilkey, Professor Emeritus of
Geologyat Duke University, whose work I have highlighted
several times in this blog. The documentary can be viewed in its entirety at
http://www.arte.tv/guide/fr/046598-000/le-sable-enquete-sur-une-disparition –
in French, but it has been taken up by PBS in the US, so watch out for the
English version being broadcast. Originally titled Sand Wars, it does a
great job of raising awareness of an environmental issue rarely brought to the
public’s attention – the way that we exploit our unsung hero is not
sustainable.

May 24, 2013

“One grain of sand, it is all that remains of my vast empire." This line is
from the classic film The Never Ending Story. When the mythical land of Fantasia
is destroyed, the protagonists are able to wish it back into existence using
that one grain of sand, which had escaped destruction. If I could have wished
Rockaway back to normal using sand I would have been in luck. Because of our
sand? Instead of disappearing it climbed into our houses, streets, cars, beds,
bathtubs and just about every other imaginable place.

As Memorial Day
approaches one can feel the return to normalcy knocking at the door. Some of the
signs of destruction haven't quite left us yet, although more and more our
hometown is starting to feel like itself again.

One of the ways that I kept my head through the storm and the winter months
that followed was by remembering what I love most about living here. The beach.
Every morning, I walk the shoreline with my pooch. Today I invite you to join
me, to see what we find in the sands of Rockaway.

Our first find, a paper plate with a child’s drawing on it.

Next, Nina and I encountered this guy, in quite a compromising position.

It’s a bit of a hobby of mine to rescue horseshoe crabs that end up flipped over
and helpless. After he was vigorously sniffed, he was re-released into the wild

Next up, this purple broom head.

Lines in the sand that remind me of tree branches.

A series of seashells and sea glass.

A little patterned feather.

And a shred of yellow caution tape.

So there you have it, the best of one morning’s exploration in the sand along
the shore. And should the day ever come when I can wish upon a sand grain, I’ll
be in luck. Right now, there are about a thousand of them in my shoes.

[As I wrote in my previous
post on the rebuilding of Breezy Point, Susanne, a resident of neighbouring
Rockaway, contacted me about using Larry Deemer’s photos on her Rockaway Rises blog (which she started
because she “was tired of looking at all the negative news stories and
photography about Rockaway.” Larry was, of course, delighted, and Susanne used
some of his Wave to Wave photos from his book
of the same title. It also seemed like a great opportunity for a guest post, and
Susanne kindly agreed – this is the very enjoyable result. Susanne grew up in
Breezy Point and is a freelance photographer and photo editor who “spent several
weeks after Hurricane Sandy digging out my parents’ flooded basement before
driving to Florida where I had to stay for 6 weeks because my office had also
been flooded and my job temporarily moved down there.” Thanks for this post,
Susanne, and best wishes for a great Memorial Day weekend to you and everyone in
Rockaway and Breezy Point.]

May 13, 2013

Back in the very early days of this blog, one of the great and rewarding
pieces of serendipity was getting to know Larry Deemer, sand aficionado and
photographer extraordinaire. I first published a selection
of his stunning images back in April 2009, and there have been subsequent
collaborations on ice,
horseshoe
crabs, and scale. And
in the meantime, he has published a glorious book of his sand pattern
images. Most importantly, also in the meantime, we have become good friends and
it’s a great pleasure to post a selection of his latest photos of the creative
conspiracy between waves, foam, and sand.

But there’s a backstory, and a dramatic one. In that first post I wrote that
Larry is “lucky enough to live in Breezy Point, a coastal neighbourhood in
Queens, the borough of New York City,” and indeed my wife and I were lucky enough to visit
Larry, Lou, and Buck and enjoy their company, their home, and their beach. But
then, in October of last year, Hurricane Sandy rolled the dice and the luck of
the residents of Breezy Point changed – catastrophically. They were hit not only
by damage from the storm (which would have been relatively manageable), but by a
devastating fire that raged out of control and destroyed over a hundred
homes. Over 200 more were terminally damaged and have been bulldozed. Larry was,
in this sense, lucky: the water damage to their house was reparable and
they have been back home since the middle of January, feeling, as Larry has
commented, “like pioneers.” But not home as it used to be – houses around them
are no longer there, and the process of rebuilding is stalled by the absurdities
of bureaucracy. We use the term “community” somewhat loosely these days, but
Breezy Point was – and is – a real community; just read some of the stories on
the web to appreciate what the word really means.

But nature continues her activities, oblivious to human hardship, and the
beach, although “the 6’ dunes are now 2’ dunes',” continues to be an
inspiration. Thanks, Larry.

[Soon after writing this post, I heard from Susanne Rieth who runs a blog called Rockaway Rises - Rockaway is right next to Breezy Point. The blog is well worth a look, described thus: "Rockaway Rises is a community for sharing and enjoying the positive aspects of life on our fair peninsula. We welcome submissions of photography, art work and uplifting stories that remind us why we love it here, and why we will continue to thrive here in spite of Hurricane Sandy. No devastation and destruction. Only gratitude for what we still have, the ocean and our community."]

April 28, 2013

The
differences in the coastal geomorphology along the Pacific coast of Tohoku in part
controlled the impact of the Tohoku-oki tsunami. a. The steep sided valleys of the Sanriku coastline
focussed the tsunami waves causing a run up height of
approximately 40 m above sea level. b.
In contrast along the low lying Sendai
Plain, the wave height was much less but it
travelled much further inland, with a maximum inundation from the shoreline of
5.4 km. Image courtesy of Kazuhisa Goto (Chiba Institute)

A couple of years ago, I wrote something of a rant on the topic of listening
to geologists in order to save lives. The post, Ignoring
tsunami records: hubris, complacency, or just human nature? was in the
aftermath of the catastrophe in Japan and reflected on what could –
should – have been learned from historical and geological testaments.
Now, thanks to a research report in Geology Today on the papers
published last year in a special issue of Sedimentary Geology, we have
a view of what has now been learned, geologically at least, in the
aftermath of the events of 2011.

The lead review paper in the journal, titled The future of tsunami
research following the 2011 Tohoku-oki event, is by Kazuhisa Goto of
Japan’s Planetary Exploration Research Center, Chiba Institute of Technology,
and the International Research Institute of Disaster Science, Tohoku University,
together with colleagues from Australia and the US. Their opening and closing
comments are worthy of attention:

The 2011 Tohoku-oki tsunami was the first example of a large, low-frequency
event occurring where historical and pre-historical tsunamis were already known
to have occurred through historical… and geological evidence... Magnitudes of
some of the historical earthquakes and their associated tsunamis had also been
estimated based on the known geological record and numerical modelling... This
point was highlighted by media soon after the 2011 event because such
information had not been taken into account in the tsunami disaster prevention
plan for the Pacific coast of Tohoku….

It is indeed true that geology is vital to gaining a better understanding of
past tsunamis along any coastline and to interpreting the hydrodynamic features
of paleotsunamis. However, the 2011 Tohoku-oki tsunami event tells us that there
is still much to be learnt from tsunami deposits if we are to produce reliable
tsunami risk assessments. Following the 2011 Tohoku-oki tsunami, we must return
to the key question – why were the results of geological studies of the AD869
Jōgan event not incorporated into disaster prevention plans in Japan? Although most
geological studies of the AD869 Jōgan tsunami had not been published in
mainstream, peer-reviewed international journals, the results were nonetheless
high quality and well disseminated. The AD869 Jōgan tsunami was indeed one of
the best studied events in the world. However, Goto et al. (2012) candidly admit
that tsunami geology is not a mature discipline and that prior to the 2011
earthquake it had not reached a sufficient level of recognition in Japan where
researchers and disaster prevention experts from various fields were interacting
effectively. Furthermore, in general terms, people continue to be unable to
comprehend the significance and relevance of extreme events that occur on
timescales spanning several 100s-1,000s of years that far exceed the human (or
building) lifespan. This is where much of the challenge lies for tsunami
scientists in education outreach to the general public.

The results that they report are fascinating, startling, and sobering – Geology Today provides a useful summary:

Future research following the 2011 Tohokuoki eathquake and tsunami

On 11 March 2011 a magnitude Mw 9.0 earthquake occurred off the Pacific coast
of Tohoku District Japan, generating a major tsunami which caused widespread
damage along the east coast of Japan and coastal areas around the whole Pacific
basin. This event, referred to as the Tohoku-oki (oki means offshore in
Japanese) generated a huge tsunami, with a run up height of up to 40 m,
resulting in 15,868 dead and 2,848 missing, along with substantial damage,
including that at the Fukushima Daiichi nuclear power plant. The damage and
death-toll was despite the fact that the Pacific coast of Tohoku was one of the
best prepared for a tsunami in the country. However, the event has also allowed
researchers to look at the effects of this very well documented tsunami and to
enable them to better interpret the historical sedimentary record to re-evaluate
the magnitude of previous events. Such work is very important when developing
tsunami disaster prevention plans.

Recently a special issue of the journal Sedimentary Geology has been devoted
to the ‘2011 Tohoku-oki tsunami’. This special issue comprising 15 papers based
on surveys and numerical modelling in Japan, along with one paper on the effects
of the tsunami in the USA is prefaced by a review article by Kazuhisa Goto and
colleagues looking at the sedimentological effects of the tsunami, future
research arising from this event and also the social relevance of this research
in the aftermath of the tsunami (Sedimentary Geology, 2012, v.282, pp.1–13).

The Pacific coast of Tohoku is divided into the Sanriku ria coast in the
north and coastal plain areas such as Sendai in the south. The Sanriku coast is
characterised by narrow drowned valleys, which have been damaged by tsunamis
every few tens to hundreds of years [header image]. In contrast the Sendai
plains are an alluvial lowland, with a beach, coastal dune ridges up to several
metres high covered by pine forests, and low lying former wetlands and rice
paddies. In this area there is no historical record of large tsunamis over the
last thousand years, except for one possible event in 1611, although small
tsunamis are recorded. These differences in the coastal geomorphology had marked
effects on the tsunami wave. On the Sanriku coast, its steep and narrow valleys
focussed the wave, generating the largest run ups, with a maximum rise of 40.4 m
above sea level, although the inundation distance inland was relatively short,
being generally up to 2 km. In contrast on the Sendai Plain, the tsunami
travelled up to 5.4 km inland, but the wave height reached a maximum of only
about 19 m. In the offshore area, about 1 km from the coastline, video footage
has allowed a flow speed of 14 m/s to be calculated, although near Miyako
sequential photographs taken from high ground suggest that the incoming wave
velocity may have reached 32 m/s. In contrast, on land the flow speeds are
variable as a result of the surface conditions, with estimates ranging between 3
and 8 m/s.

Sediment
deposits from the tsunami included deposits of sand and mud across the Sendai
Plain, along with gravel deposits and locally extremely large boulder deposits.
Image courtesy of Kazuhisa Goto

Following the tsunami, rapid geological surveys were conducted to gain an
understanding of the types of sedimentary deposits resulting from an event of
this magnitude. On the Sendai Plain a sand layer extended some 3 km inland which
continued as a mudstone layer almost to the maximum inundation limit of 5.4 km
[image above]. This unit reached a maximum thickness of 30 cm and generally
thinned inland. This bed was typically parallel laminated or structureless sands
and silts with fragments of wood, glass and ripped up mud clasts overlying an
erosional base. Based on an analysis of its heavy minerals, microfossils and
isotope chemistry, it appears that most of the deposited sediment on the Sendai
Plains was derived from beach, sand dune, lagoon and inland soils with only a
minor contribution from offshore sediments. Importantly, it was recognized that
a lot of the sediment resulted from liquefaction, with sand being vented from
beneath the soils in the rice paddies. In contrast, on the Sanriku coast, the
deposited sediment comprised both the eroded beach sands but also marine
sediment from both the inner bay and even more pelagic areas.

In addition to the deposition of sands and muds, granule to boulder sized
clasts were also observed. In some cases gravel deposits were up to 1 m thick
and thinned landward. Boulder deposits were also observed, including large
reworked fragments of concrete from the coastal defences, with the largest
observed natural boulder being 6.5 × 2.5 × 2.4 m in size.

Offshore, within coastal bays and harbours there was evidence for both
erosion, but also sediment deposition with the formation of large-scale
submarine dunes. Further offshore at water depths between 300 and 5940 m the
seafloor was covered by muddy sediments, in areas that prior to the earthquake
had sandy or gravel surfaces. These sediments are interpreted as the deposits of
turbidites, resulting from the tsunami backwash. Other turbidite deposits
between 1 and 25 cm thick were observed in cores recovered offshore from the
Sendai and Sanriku coastline, and caesium-134 and caesium-137 released from the
Fukushima-Daiichi nuclear plant was detected on the top of these deposits.

Such sedimentological studies as these are critical for us to correctly
interpret the ancient record of past tsunami events, which in turn help us
understand the scale and frequency of past events. This is indispensable in
developing tsunami risk assessments, and the improvement of disaster prevention
measures.

[I have to admit that I refrained from commenting that Kazuhisa Goto was the
guy they should have gone to when planning tsunami defences, but it seemed – and
probably still is – inappropriate. His 2012 article is online in
English. The complete list of all the papers in the journal can be found at
http://www.sciencedirect.com/science/journal/00370738/282.
The full articles are behind the pay wall, but I will be happy to supply a PDF
for personal use if any reader would be interested.]

April 02, 2013

A sand scandal is brewing in China, with concerns that low-quality concrete
has been used in the construction of many of the country's largest buildings --
putting them at risk of collapse.

The recipe to make concrete is pretty simple -- cement, aggregate and water
-- but the strength of the final batch can vary wildly depending on the kinds of
aggregate and cement used and the proportions they're mixed in. Commonly the
aggregate used in many modern buildings projects consists of crushed gravel or
other rock, including sand, and that's the cause of so much distress in the
Chinese construction industry at the moment. Inspections by state officials have
found raw, unprocessed sea sand in at least 15 buildings under construction in
Shenzhen, including a building which, when finished, was set to become China's
tallest.

The Ping'An Finance Centre is planned to top out at 660m, making it not only
China's tallest building but the second-tallest building in the world after the
Burj Dubai. 80m has been built so far, but construction has been halted in the
wake of the revelation from Shenzhen's Housing and Construction Bureau that
substandard sea sand concrete had been used in its construction. According to a
notice on the
Bureau's website posted on 16 March, 31 companies had had their licenses to work
revoked for at least six months…..

It can take only a few decades for a building to become dangerously unsafe if
untreated sea sand is used in its concrete -- including the possibility of
collapse. While this scandal has been confined only to Shenzhen thus far, the
possibility of it spreading to other Chinese cities is worrying. The country
currently has nine
of the 20 tallest buildings in the world that are under construction, while
there were reportedly so many skyscrapers under construction in 2011 that it
worked out as a new one being topped out every
five days right through into 2014.